A fluid machine is known in the conventional technology which includes a single casing containing therein a compressor and an expander (see, for example, JP-A-2003-172244). The fluid machine disclosed in JP-A-2003-172244 is used in a refrigerant circuit of an air conditioner.
The refrigerant circuit of the air conditioner is made up of a compressor, a cooler, an expander, and an evaporator which are connected by piping. In the refrigerant circuit, refrigerant is circuited whereby a vapor compression refrigeration cycle is performed. That is to say, refrigerant compressed in the compressor is cooled in the cooler, expanded in the expander, evaporated in the evaporator, and returned again back to the compressor. And, the compressor and the expander are coupled together through the driving shaft of an electric motor. Stated another way, the compressor and the expander are connected together by a single rotating shaft.
In the fluid machine, power is generated by the expansion of refrigerant in the expander and the generated power is transmitted, as rotational power, through the driving shaft to the compressor. By means of this, the load of the electric motor is reduced.